The objectives of the research are to determine the effects of psychomotor stimulants such as cocaine, methylphenidate, and amphetamines on intraspecies aggression and defensive-submissive reactions, and on predatory aggression in rats, mice and squirrel monkeys. Specifically, a resident-intruder paradigm will be employed which has been validated to generate sequences of species-specific intense aggressive interactions in all three species. Predatory aggression will be studied in the form of the mouse-killing reaction of the rat. Drug effects are measured for the characteristic acts and postures involved in interactions between attacking and defensive-submissive animals as well as between prey and predator. The data analysis is designed to give information on drug effects on frequency, duration, temporal pattern and sequence of clearly identifiable aggressive, defensive-submissive, and non-aggressive behavioral elements. The importance of several pharmacological variables will be assessed, including dose, route of administration, acute and chronic administration. The sequential analysis of the salient aggressive and non-aggressive motor activities is expected to reveal potentially "disruptive" and "disorganizing" effects of psychomotor stimulants on complex multi-component sequences of behavior.